This invention relates to fuel injection piston engines and is concerned with improving the performance thereof of liquid hydrocarbon fuelled, spark ignition piston type internal combustion engines.
The invention is particularly applicable to such engines wherein gasoline is the fuel. However, other liquid fuels, such as alcohol, could be used.
In most fuel injection systems employed by such engines, fuel is injected into the engine air induction tracts or air inlet valve ports downstream from the engine throttle(s).
To-day it is common practice to use fuel injectors in which a solenoid operated valve is opened in response to signals received from a computer-controlled electronic control unit (ECU). The injectors are supplied with fuel maintained at a substantially constant pressure.
The computer controlled ECU varies the frequency and duration of the injector valve opening in response to inputs which indicate such data as throttle position, engine speed, manifold depression and the temperatures of the intake air, coolant and fuel. Additional control parameters may be used including the measurement of mass air flow.
In a multi-point sequential injection system, fuel is injected into the engine so as to coincide with TDC (Top Dead Centre) or soon after TDC. The duration of the injector valve opening is determined by the ECU in accordance with the total volume of fuel required by the engine at any given time. A fundamental weakness of this system however, is that the duration of the fuel spray is not directly related to the length of the engine's air induction phase, with the result that air will continue to flow into the combustion chamber after the injector has ceased to spray. This continuation contributes to the formation of a non-homogeneous air/fuel mixture.
It is this defect that has led to disappointing results, in securing improved fuel consumption and reduced exhaust emissions, when currently available multi-point sequential systems have been adopted.
According to the present invention, a sprayer for a fuel injection, spark ignition, piston type internal combustion engine comprises a hollow casing, and means for injecting liquid fuel into the hollow interior of the casing, with structure placed within the hollow interior of the casing and disposed in the path of fuel injected, characterised in that the structure is formed whereby injected fuel is deposited on said structure, so that the induction phase of the engine causes the deposited fuel to be removed from said structure and into the engine, and in that casing outlet means are provided, comprising a venturi-shaped passageway, the inlet end of which is disposed downstream of and spaced from said structure, and operable to mix air and liquid fuel together before the mixture leaves the sprayer.
U.S. Pat. No. 4,674,460 discloses a sprayer having the features of the non-characterising portion of this statement of invention. However, this reference does not make it clear that fuel is indeed deposited on structure in the path of injected fuel and is indeed caused to be subsequently removed by the induction phase of the engine.
The term "induction phase" is used herein and is intended to include "induction stroke", as the induction stroke of the engine may not coincide entirely with the induction phase of the engine. The induction phase may, for example, begin before TDC (top dead centre) and finish after BDC (bottom dead centre).
The structure placed within the hollow interior of the casing preferably comprises an inner body disposed with an outer body of annular form, so as to define an annular passageway therewith.
Alternative structure may comprise a sheet of gauze disposed substantially normal to the path of fuel injected.
The body outlet preferably defines a venturi-shaped passageway, which may function as a sonic nozzle.
The invention also comprises a fuel injection, spark ignition piston type internal combustion engine provided with said fuel sprayer.